Effects of Mandibular Deviation on Brain Activation During Clenching: An fMRI Preliminary Study

Abstract

Using functional magnetic resonance imaging (fMRI) in eight healthy human subjects, the present study measured blood oxygenation level-dependent (BOLD) signals during clenching in a malocclusion model, using a custom-made splint that forced the mandible to a retrusive position and a splint of no modification for control, and compared the results to the BOLD signals during the corresponding resting conditions. An individual visual analog scale (VAS) score was also examined during clenching to evaluate the interactions between fMRI data and psychiatric changes. During both clenchings, activations in four brain regions (premotor cortex, prefrontal cortex, sensorimotor cortex, and insula) were seen. However, clenching in the malocclusion model, with psychological discomfort, increased additionally BOLD signals in the anterior cingulate cortex and the amygdala. Furthermore, there was a parallel relationship between BOLD signal intensities and VAS scores in these two regions. The findings may suggest the involvement of clenching with malocclusal conditions in the emotion and/or pain-related neural processing in the brain.

Masticatory function and cognitive function

“…Otsuka et al measured BOLD signals during clenching in a malocclusion model using a custom-made splint in humans and reported that malocclusion affects emotion-related neuronal processing in the brain, such as in the anterior cingulate cortex and amygdala 61) . The occlusal disharmony-induced changes in the hippocampus are due largely to stress responses.…”

Effects of orthodontic reconstruction on brain activity in a patient with masticatory dysfunction

“…Brain function was analyzed before orthodontic treatment with and without the occlusal splint and after orthodontic treatment using exactly the same procedure as in a previous fMRI study [11]. Briefly, a 1.5-T Horizon MRI scanner (PHILIPS, InteraAchiva) first produced functional images (T2*-weighted) and then an The SPM5 software (Wellcome Department of Cognitive Neurology, London, UK) was used to correct for inadvertent head motion.…”

“…A human study also showed that mastication and teeth clenching prevent stress-induced amygdala activity in the brain [14]. Recently, it was reported that experimental posterior displacement of the mandible induced significant activity in the limbic system [11] suggesting that mandibular displacement due to malocclusion, such as unstable intercuspation or poor posterior vertical support, may be associated with somatic symptoms.…”

The Amount of TMJ Displacement Correlates with Brain Activity

“…[1][2][3][4] These studies indicate that occlusal dysfunction affects the stress response via brain function and leads to non-oral health problems. Experiments with human subjects have shown that posterior mandibular displacement significantly activates the limbic system, 5 indicating that occlusal dysfunction causes various somatic symptoms. Functional MRI is a useful noninvasive tool for testing specific hypotheses regarding the anatomical regions that process sensory and motor signals in the brain.…”